1. Technical Field of the Invention
The present invention relates to input devices, such as keypads and keyboards, as well as to displays and the like, and in particular, to backlit keypads, keyboards and displays utilizing electroluminescent polymers.
2. Description of Related Art
Backlit input devices, such as keypads and keyboards, and displays are known in the art. These devices typically include a light source transmitted either through or underneath a pad or board including operation keys, such as those found on a typewriter or ten-keypad, to provide an optical contrast against the keys. Applications for such backlit input devices include uses in persistent low-light environments (e.g., air traffic controller booth, submarine) and in devices capable of use at night or indoors (e.g., cellular telephone).
Prior art backlit input devices include keypads of generally two types: devices where the keys are constructed from light-transmitting material and devices where conduits or channels are used to conduct light from a source to the keys. In the former, the keys and underlying pad or board are typically molded as a single piece and then placed over or adjacent to a light source. In the latter example, devices in which conduits or channels are used to transmit light from a source to the keys, conduits such as fibers offer tight control over the level of light transmitted. Backlit displays include traditional light-emitting diode (LED) displays, liquid crystal displays(LCD), and the like.
Regardless of the type of construction, however, the light source for the prior art devices is typically separated from the keys or display surface, requiring additional space in which to store the light source and the mechanism for transmitting light from the source to the keys or display surface. This separation also requires a relatively powerful light source so that the keys and/or display surface are sufficiently backlit despite the loss of some of the light during transmission from the source. Stronger light sources typically require additional space, increased power requirements and generate excess heat, all adversely affecting design options for such device. The need for access to the traditional light sources (e.g., for replacing or maintaining the light source) used in prior art devices presents additional design limitations.
Thus, a backlit input device, such as a keypad or keyboard, having a light source which is closely associated with the keys, utilizes a relatively low powered light source, and does not require special space and/or design limitations, is desired. The prior art of backlit keypads, keyboards and displays does not suggest that a backlit device having a light source which is closely associated with the keys or display surface, uses a relatively small amount of space and power, and not requiring conduits or channels to transmit the light from the source to the keys or display surface, is possible.